Heat pump



Sept. 20, 1955 D. c. PRINCE 2,718,119

HEAT PUMP Filed Deo. s1, 1952 i i aars/0E AM? i @Mawr/Pof United States Patent HEATPUMP David C. Prince, Schenectady, N. Y.

Application December 31, `1952, Serial No. 329,005

17 Claims. (Cl. 62-3) This .invention relates to vheat pump systems and more particularly to the control of such systems.

.Heretofore heat pump systems .have been designed for constant speed .start-.stop operation in response to changing heat load conditions requiring .that the operating speeds of both the .refrigerant compressor and the .circulatingfans for .the evaporator and capacitor be great .enough to meet the lrequirement of the most severe duty required thereof. In a favorable .geographical location, operating in the above manner, it is .possible .to .approach 2.8 as a coefficient of performance, defined as the ratio of .the output heat lunits delivered to the input heat unitssupplied as electrical power. .'By modulating the compressor :so that .its output is reduced -at lighter loads, .itis possible to .increase slightly the coeiicientrof performance, .but the overall gain realized in this manner .is limited .by .the power required to drive .the fans which at light loads becomes the dominating factor. The vdelivery of the compressor is .a functi'onof the first power of its speed whereas the .delivery of the fans varies as the square of their speed .so that vfor -opt-imum operating conditions, Vthe .relative reduction of the fan :speed under lighter load conditions should be less than speed reduction of the compressor.

Objects of this invention are to ,provide a heat pump system which has a high Acoefficient of performance, Vwhich has a .high etciency, which y.permits speed of the acompressor and fans to be varied simultaneously, which jper- .mits a relatively ygreater change in the .speed of the 1Compressor than in the `speed of -the fans, which .is responsive to changes .in a 'control temperature, which provides a temperature modulated ilow of heat, which risautoma-tic -i-n operation, which can be adapted for use with existing equipment, and which advances the art generally. A.'fur ther object is to provide ya Vspeed regulating system whereby it is .possible to vary conjointly lthe speeds of Vtwo output loads.

.A .heat :pump system according tothe .present invention comprises a compressor which .is Aconnected in series :with two heat exchangers that act respectively as a condenser andan evaporator. The compressorand thefans oriother circulating means for causing `ambient: .fluid :to pass over the heat .exchangers are driven .by .means whereby lthe speeds Ithereof `vary as functions 'of a control ltemper- Vature, `the speed variation of the .compressor preferably being materially greater than 'the speed variation fof the fans Afor a given change in .the .cont-rol temperature. .In another aspect the compressor fand .fans impose 'output loads upon a speed changer such as ya fcompound pull'ey, which'is driven from afcommofn input power .source such :as aprirne mover.

These and other objects and aspects lof .the invention will lbe 'apparent from the fol-lowing description 'of a 'speci'c embodiment `of the iinventionwhich refers tofa drawing wherein: K

Fig. '1 is fa schematic :diagram :of .a rheat pump; and

Fig. 42 is 'a side vview of a .compound 'pulley 'for use 'the fsys'tern.

As is shown in Fig. 1, the heat pump system comprises ICC a vrefrigerant compressor 10 which may be of `any ofthe well known vcommercially available types. The-compres- -sor 10 .is connected .in series with two heat exchangers I2 and l14 by .means .of fluid-tight lconduits such .as the tubing 16. An .expansion valve 18 is :interposed in the tubing 'connecting -the heat exchangers 14 and 16 .so that they act respectively as `a condenser and an evaporator when a refrigerant is circulated Atherethrough yby the compres- 'sor 10.

Thec'ondenser 12 andthe evaporator A14 vare enclosed in a ductwork system 20 which is provided with four dampers 22. With the dampers 22 .in .the position shown in Fig. l, -air from inside an enclosure such as a building or rhouse '(not shown) is circulated through .the .condenser 12 hy a 'fan 24 so vthat .heat from the condenser is used for heating ythe interior of the enclosure. A `second fan .26 simultaneously circulates outside vair .through `the evaporator .14 to increase the temperature of the .refrigerant to add heat .to the system. When the outside lair temperature exceeds .that desired :in :the interior lof the enclosure fthe dampers 22 are'transferred either manually tor automatically to the positions shown by `broken lines in Fig. .1, whereby the heat from the condenser 12 is dissipated outside and the inside .air passing through the evaporator 14 is `cooled so f that the system .acts vas an air conditioner.

"The 'fans .24 and 26 are :operated from a-common drive .including shaft 2:8 and beveled gears 30. The shaft .28 is connected with a sheave 32 by meansof an intermediate shaft 34 and two pairs of beveled gears 36 and 38 .located respectively at either end thereof. The sheave 32`is driven v.from a prime mover such as -the motor M by means of 'a :simple .pulley 39, a V-.belt 40, `'a speed changer including ta variable vcompound pulley 42 and a pulley shaft 44 'which is displaceable in a radial direction vas will .be der scribed 'indetail below, a mating Lsheave 46 attached to the pulley shaft and a V-belt 48. The im'otor vM also :acts as the common powerisource for the .compressor 10, a 'simple pulley 50 yon 'the compressor Vshaft being connected with the y.compound pulley 42 by a V-b'elt 52.

As is best shown in Fig. .2, Iin which the belts 40 kand 52 are not delineated, the compound pulley 42 comprises two spaced sheave portions 5'4 and 55 which are relatively ixed to the .shaft 44 by means of keys yor set screws (not shown). interposed :between the fixed `sheave portions 54 and 1S5 is a 'movable sheave portion 56 which .is .slidable yaxially along .the vshaft 44. The V-belt 40 from .the motor pulley 139 is interposed .in the V-notch formed by the fixed .sheave portion .'54 `and the slidable sheave portion 56,1thee`ffe'ctive diameter ofthe driven sheave formed thereby .and the speed of the lshaft 44 'being .determined by the faxial position of the slidable sheave'portion, it being evident .that :as the slidable sheave portion is :moved 'towards the vfixed sheave portion, the effective sheave diameter fis :increased andthe .resulting driven sheave rol-tates lt-he 'pulley shaft l44 at a slower speed. Conversely, uas .the 'slidable .sheave portion 56 .moves away from 'the vfixed `sheave portion 521, the eifective rsheave diameter 'is decreased .and '.the shaft speed is increased. The :movement of the slidable sheave portion 56 has the opposite .etiect'to ythatdescribed above Aupon the sheave :formed by the .'slida'ble sheave portion :56 4and the 'fixed sheave "por- -1tion 55 wherein Nis 'carried `the V-belt 52 .for driving the .compressor '10, i. e., as .the effective 'diameter ofthe `first fsheave :driven zby the motor M .is increased (or decreased) 'the effective :diameter 'of "the .second lsheave driving the 4compressor'decreases '('or increases) correspondingly. As 'the first sheave is 'driven :and the 'second sheave is driving,

lt-heir effect upon the speed ofthe vcompressoris cumulative and ,it-is possible .to obtain a -4 to l variable speed ra-nge of 'the shaft t44 driving the fans with a corresponding .'16 to -l variable speed yrange of `the compressor 110.4

The axial position of the slidable sheave portion 56 is controlled by the swinging of the pulley shaft 44 in a large arc'which imparts a displacement to the shaft 44 and attached pulley 42 thereby tightening one of the belts and slackening the tension in the other belt, the particular belt being tightened depending upon the direction in which the displacement of the shaft 44 takes place. The reaction force to the belt tension is supplied by the inclined faces of the corresponding sheave portions which are inclined so that there is an axial force component which tends to separate the movable sheave from the stationary sheave. As the other belt is conjointly slackened there is no opposing force so that the slidable sheave portion moves until it reaches a position of equilibrium which corresponds-to the particular displacement of the pulley shaft 44.

The above mentioned displacement which results in a substantially radial movement of the shaft 44 is obtained by journalling the shaft in bearings in a bracket 60 which is pivotally mounted as at 62. The bearing bracket 60 is rotated about its pivot point 62 by a gear segment 64 whose teeth mesh with a pinion 66 upon the shaft of a reversible control motor Ms. A source of direct power such as the battery B is used to energize the control motor Ms. To this end one terminal of the battery is connected to the motor Ms through ground. The other battery terminal is alternatively connected to the separate reversing windings of the motor Ms by contacts C1 and C2, respectively, of a thermostat T which is located so that its bimetallic element S is subject to a control temperature, for example, the ambient air within the enclosure. The closing of the contact C1 when the ambient temperature exceeds the control temperature, energizes the winding of the control motor Ms which results in a movement of the shaft 44 in a direction to tighten the belt 52 and slacken the belt 40, as described heretofore, thereby to slow down the compressor and to decrease the heat output of the system. The fans 24 and 26 are also slowed down but because of the action of the compound pulley 42 the reduction is proportionately less thereby to accommodate the reduced heat output.

Conversely, when the ambient temperature falls below the control temperature the contact C2 closes to reverse the motor Ms to move the shaft 44 in a direction to tighten the belt 40 and the belt 52 slackens so that the speed of both the fans and compressor 10 are increased to raise the heat output of the system. lf the ambient temperature is only a little below the control temperature the heat from a heater resistor R located adjacent the bimetallic strip S will cause the contacts to open before there has been much movement of the gear segment 64. The ratio of the pinion 66 and the segment 64 is made low so that the movement of the bearing bracket 60 is slow and the change in the heat output of the system is not materially effected until the drop in ambient temperature is sufficient to overcome heating effects from the resistor R.

The above describedsystem provides a steady ow vof heat which is modulated so as to avoid abrupt changes in temperature at the same time increasing the co-eicient of performance to a value of 8 or 9 which represents a material gain in the overall efliciency. A corresponding gain is realized when the system is used for cooling when the dampers 22 are moved to the dotted position.

I claim:

l. A heat pump system comprising two heat exchangers, refrigerant circulating means connected in series with the heat exchangers whereby the refrigerant is forced therethrough, an expansion valve interposed between said heat exchangers so that they act respectively as a condenser and an evaporator for the refrigerant, further circulating means for causing ambient iluid to pass over the heat exchangers, variable speed driving means operating each of the circulating means over a range of speeds, and control means for the driving means which is responsive to changes in a control temperature to vary the speeds of the circulating means respectively as functions of the control temperature, the variation in the speed of the refrigerant circulating means being materially greater than the variation in speed of the ambient fluid circulating means for a given change in the control temperature.

2. A heat pump system comprising a refrigerant compressor, two heat exchangers connected in series with the compressor whereby the refrigerant is forced therethrough, an expansion valve interposed between said heat exchangers so that they act respectively as a condenser and an evaporator for the refrigerant, means including one or more fans for selectively circulating either indoor or outdoor air past said heat exchangers, variable speed driving means for operating the compressor and fans over a range of speeds, and control means for the driving means which is responsive to changes in a control temperature to vary the speeds of the compressor and fans respectively as functions of the control temperature, the variation in the speed of the compressor being materially greater than the variation in the speed of the fans for a given change in the control temperature.

3. A heat pump system according to claim 2 wherein the driving means includes a common prime mover to drive both the compressor and fans.

4.l A heat pump system according to claim 3 wherein the prime mover is operated at a substantially constant speed and speed changing means responsive to variations in the control temperature are interposed between the prime mover and the compressor and fans.

5. A heat pump system according to claim 4 wherein the speed changing means causes a materially greater variation in the speed of the compressor than in the speed of the fans for a given change in the control temperature.

6. A heat pump system according to claim 5 wherein the speed changing means includes a variable speed pulley.

7. A heat pump system according to claim 6 wherein the variable speed pulley is a compound pulley and the Yshaft whereupon the pulley is mounted forms a portion of the driving means for the fans.

8. A heat pump system according to claim 7 wherein the variable speed pulley includes a movable sheave portion which is arranged to slide axially upon the pulley shaft and two relatively xed sheave portions which are attached to the pulley shaft upon either side respectively of the movable sheave portion thereby to form two sheaves whose effective diameters are varied inversely by the axial movement of the movable sheave portion.

9. A heat pump system according to claim 8 wherein the speed changing means includes two belts which interconnect the prime mover and compressor with the respective sheaves of the compound pulley.

l0. A heat pump system according to claim 9 wherein means are provided for displacing the pulley shaft in a substantially radial direction in response to changes in a control temperature.

l1. A heat pump system according to claim 10 further including a pivotally mounted bracket having bearings wherein is journalled the pulley shaft so that the shaft is displaceable in a substantially radial direction.

l2. A heat pump system according to claim ll further including a reversible motor for moving the bearing bracket about its pivotal mounting in either direction and a thermostat for controlling the operation of the motor so that a temperature change results in the movement of the bracket and a change in the effective diameter of the sheaves thus varying the speed of the compressor and fans.

13. A drive for regulating the speed of two separate loads comprising an adjustable compound pulley having two sheaves whose effective diameters are inversely variable, a shaft for connecting the compound pulley with one of the loads, two simple pulleys each of which is mounted upon a respective shaft, the shaft of one simple pulley being connected to the other load, the shaft of the second simple pulley being connected to an input power source, a belt connecting each of the simple pulleys with a respective sheave of the compound pulley, and means for adjusting the eiective diameters of the sheaves of said compound pulley conjointly to vary the speed of the output loads whereby for a given speed of the input power source adjustment of the compound pulley causes a materially greater change in the speed of the load connected to the simple pulley than the change in speed of the load connected to the compound pulley.

14. A drive for regulating the speed of two separate loads according to claim 13 wherein the compound pulley comprises a movable sheave portion which is arranged to slide axially upon the shaft and two relatively fixed sheave portions which are attached to the shaft upon either side respectively of the movable sheave portion so that the effective diameters of the sheaves formed thereby are varied inversely by the axial movement of the movable sheave portion.

15. A drive for regulating the speed of two separate loads according to claim 14 wherein the compound pulley and its correlated load are journalled in a bearing bracket which is pivotally mounted to displace the shaft in a substantially radial direction thereby to cause the movable sheave portion to slide axially thus changing the speeds of the respective loads.

16. A drive for regulating the speed of two separate loads according to claim 15 wherein a reversible motor is connected to move the bearing bracket in response to an input signal.

17. A drive for regulating the speed of two separate loads according to claim 16 wherein the input signal source is a thermostat.

References Cited in the ile of this patent UNITED STATES PATENTS 1,942,295 Kerr Jan. 2, 1934 2,045,870 Paton June 30, 1936 2,219,184 Herman Oct. 22, 1940 2,308,507 Hallinan Ian. 19, 1943 2,392,226 Butterworth Jan. l, 1946 2,486,524 Dulaney Nov. l, 1949 2,549,637 Reeves Apr. 17, 1951 2,637,175 Alexander May 5, 1953 FOREIGN PATENTS 89,666 Switzerland June 16, 1921 

